About the border color, the module allows you to set the same attributes especified at https://developers.facebook.com/docs/reference/plugins/like-box/
I have just noticed that there are a couple of them more (force_wall and show_border) so I will prepare a new release with these new attributes when I have some time. However, about the colour itself, it might be possible to override it in your especific theme as a CSS property (I have not tried myself).

I am going to be pretty busy these days (working on a PhD proposal), but I will try to take a look asap. Any patches are very welcome as well!

I have just made a quick test with Firebug, and if I am referring to the same icon, the property should be ._rw (find attached a screenshot). Please let me know if you successfully override it in your own theme.
Hope this helps!

David, I noted above (#3) that the only thing this module doesn't support that fb_social does support is changing the border color. Going further on what I said at https://drupal.org/node/2018011 (#3), I guess there are some things Facebook allows you to change that CSS can't override. We know for a fact that the border color can be changed, so I just want you to double-check & see if Facebook also allows you to change the size of the default icon. If yes, great. If not, any idea on other ways to do this (Javascript)? Any pointers would be great.

P.S. Focus on your PhD. I'm not in a hurry & won't be offended if you reply late.